1. Field
This disclosure is concerned generally with flexible plastic bags used for collecting, processing and storing of blood and blood components. The disclosure is especially concerned with a blood bag found useful for separating and isolating red cells on the basis of their relative ages using density gradient separation techniques.
2. Prior Art
The manufacture and use of flexible, plastic containers (bags) for the collection, processing and storage of blood and blood components is well known. Whole blood from a donor is typically obtained via venipuncture and collected via tubing in a so-called donor bag. The donor bag may or may not be connected via tubing to one or more so-called satellite or transfer bags. When connected to at least one transfer bag, the donor/transfer bag combination is commonly referred to as a "multiple" blood bag system which may include one, two, or three transfer bags, all in sealed communication with the donor so that, once blood or blood components are introduced into the system, the whole blood or its components may be moved from one bag to another by external manipulation (of valves, etc.), thereby avoiding or minimizing contamination.
In a typical multiple blood bag application, whole blood collected into a donor bag and the connected but empty transfer bag(s) are placed in a centrifuge cup designed to hold the filled donor bag in a generally upright position. The bag contents are then centrifuged to separate whole blood into its lighter serum component and its heavier red blood cell component. By manipulating a valve (usually within the system), the upper plasma may then be expressed into one of the transfer bags, possibly for further processing (e.g. into platelet-rich and platelet-poor components which may be expressed into other connected transfer bags). The separated platelet-poor plasma component may be subsequently fractionated into a variety of other products useful in so-called component therapy (clotting factors, immune serum globulins, albumin, etc.).
In the first separation of plasma from red blood cells in a centrifuged donor bag, the upper plasma portion is often removed from the donor bag using a relatively simple device known as a plasma expressor. The expressor simply squeezes the donor bag, until the plasma is fully expressed out of the bag, typically into a connected transfer bag. At this stage, the separation is fairly approximate and a fine line of demarcation separating the plasma from the packed red cells is generally not critical. In subsequent separations, however, finer separations do become important.
In patent application Ser. No. 585,793 filed in the names of S. Wada et al on Mar. 2, 1984 and entitled, "Container for Fine Separation of Blood and Blood Components", a blood bag for separating white blood cells from platelets is shown. In that disclosure, a conventional blood bag is modified at the bottom to provide a small receptacle for collection and isolation of white blood cells (WBC) from a platelet/WBCs mixture. That disclosure focuses on minimizing the interface between the separated platelets and WBCs by carefully controlling the volume and dimensions of the continuous receptacle and providing a centrifuge insert adapted to accommodate the bag and receptacle.
In U.S. Pat. No. 3,911,918 issued to Turner, there is disclosed an hour-glass shaped plastic blood bag comprising several compartments for the separation and isolation of blood components. That bag is capable (after component separation) of being separated to form a number of individual storage compartments for the separated components. As pointed out in that patent, prior art blood storage containers previously had not been detailed in size and shape to contain a predetermined quantity of blood or a blood component (such as plasma) in separate compartments.
More recently in U.S. Pat. No. 4,416,778 to Rogers, there is disclosed a dual compartment plastic blood bag in which the two compartments are connected via a tubing. The tubing includes a valve adapted to open only after a given centrifugation force is obtained. The bag is said to be especially useful for separating less dense and relatively younger red blood cells (neocytes) from more dense and relatively older red blood cells (gerocytes). As pointed out in that patent, the teachings of which are incorporated herein by reference to it, the use of neocytes is thought to be useful in minimizing iron overload possibilities in patients who depend on repeated blood transfusions.
To date, the primary method used for separating various blood components is simple centrifugation using blood bags (either conventional bags or specially designed bags such as those shown in the above patents) or a specialized mechanical apparatus. One apparatus useful for separating blood components, including neocytes and gerocytes, is an instrument known as an IBM Model 2991 blood cell separator.
Unfortunately, the bags and apparatus available for fine separation of blood components tend to be fairly complex and expensive, thus limiting their use. We have investigated various ways of providing simpler, less costly methods and devices for the separation and isolation of blood components, especially the separation of neocytes and gerocytes. Quite surprisingly, we found that by making relatively inexpensive modifications to conventional blood bags, we can obtain blood component separation and isolation comparable to that obtained using specially designed and complicated bags or specialized and costly machines. Details of our bag are disclosed below.